Tetrapyrrole compounds
Tetrapyrrole compounds: chlorophyll and heme groups
By Erwin Lim
1. Tetrapyrrole compounds
A tetrapyrrole compound is a chemical group that consists of four pyrroles that are joined together by covalent bonds, forming a porphyrin ring. They are naturally occurring pigments, which are used in many biological processes (Berg, 2009). The basic structure of a tetrapyrrole is as seen in Figure 1, while the basic structure of a pyrrole is as seen in Figure 2.
Figure 1.Tetrapyrrole Compound (Berg, 2009)
Figure 2.Pyrrole (de Man, 1999)
2 Chlorophyll groups
2.1 Definition and structures
Chlorophylls are tetrapyrrole pigments in which the porphyrin ring is in the dihydro form and the central metal atom is magnesium. They are green pigments responsible for the color of leafy vegetables and some fruits. Chlorophylls are diesters of a dicarboxylic acid (chlorophyllin), where one group is esterified with methanol at C-3, while the other is esterified with a phytyl alcohol at C-7 (de Man, 1999). They are also the major light-harvesting pigments in green plants, algae, and photosynthetic bacteria (Von Elbe as cited in Fennema, 1996). The majority of the green pigments are chlorophyll a, which is blue-green, and chlorophyll b, which is yellow-green, occur naturally in nature in an unset ratio. As shown in Table 1, there is no trend with regards to the amount of chlorophyll a and chlorophyll b present.
Table 1. Chlorophylls a and b in vegetables and fruits (Belitz, Grosch, and Schieberle, 2009)
Food
Chlorophyll a
Chlorophyll b
(mg/kg)
Green Beans
118
35
Kale
1898
406
White Cabbage
8
2
Cucumber
64
24
Parsley
890
288
Green bell pepper
98
33
Green peas
106
22
Spinach
946
202
Kiwi
17
8
Gooseberry
5
1
There are two major chlorophylls: Chlorophyll a and Chlorophyll b. Chlorophyll a differs from chlorophyll b in that the aldehyde group on carbon 3 is replaced with a methyl group (deMan, 1999). Chlorophyll c1 and c2 vary at the carbon
By Erwin Lim
1. Tetrapyrrole compounds
A tetrapyrrole compound is a chemical group that consists of four pyrroles that are joined together by covalent bonds, forming a porphyrin ring. They are naturally occurring pigments, which are used in many biological processes (Berg, 2009). The basic structure of a tetrapyrrole is as seen in Figure 1, while the basic structure of a pyrrole is as seen in Figure 2.
Figure 1.Tetrapyrrole Compound (Berg, 2009)
Figure 2.Pyrrole (de Man, 1999)
2 Chlorophyll groups
2.1 Definition and structures
Chlorophylls are tetrapyrrole pigments in which the porphyrin ring is in the dihydro form and the central metal atom is magnesium. They are green pigments responsible for the color of leafy vegetables and some fruits. Chlorophylls are diesters of a dicarboxylic acid (chlorophyllin), where one group is esterified with methanol at C-3, while the other is esterified with a phytyl alcohol at C-7 (de Man, 1999). They are also the major light-harvesting pigments in green plants, algae, and photosynthetic bacteria (Von Elbe as cited in Fennema, 1996). The majority of the green pigments are chlorophyll a, which is blue-green, and chlorophyll b, which is yellow-green, occur naturally in nature in an unset ratio. As shown in Table 1, there is no trend with regards to the amount of chlorophyll a and chlorophyll b present.
Table 1. Chlorophylls a and b in vegetables and fruits (Belitz, Grosch, and Schieberle, 2009)
Food
Chlorophyll a
Chlorophyll b
(mg/kg)
Green Beans
118
35
Kale
1898
406
White Cabbage
8
2
Cucumber
64
24
Parsley
890
288
Green bell pepper
98
33
Green peas
106
22
Spinach
946
202
Kiwi
17
8
Gooseberry
5
1
There are two major chlorophylls: Chlorophyll a and Chlorophyll b. Chlorophyll a differs from chlorophyll b in that the aldehyde group on carbon 3 is replaced with a methyl group (deMan, 1999). Chlorophyll c1 and c2 vary at the carbon
References: Belitz H, Grosch W, Schieberle P. 2009. Food Chemistry. 4th ed. Heidelberg: Springer-Verlag Berlin Heidelberg. Berg, K. 2009. Photosynthesizers in Medicine. [cited 26 February 2013] Available from: http://www.photobiology.info/Berg.html Claus JR. 2007. Color Changes in Cooked Beef. Beef [Internet]. [cited 2013 Mar 15] Available from: http://www.beefresearch.org Coultate TP. 2002. Food the Chemistry of its Components. 4th ed. Cornwall, Great Britain: International Ltd de Man J. 1999. Principles of Food Chemistry. Gaithersburg, Maryland: Aspen Publishers, Inc. Johnston CH, Schauer L, Rapaport S, Deuel jr. HJ. 1943. The Effect of Cooking with and without Sodium Bicarbonate on the Thiamine, Riboflavin, and Ascorbic Acid Content of Peas. Department of Biochemistry. University of Southern California Medical School, Los Angeles Hynninen PH. 1973. Chlorophylls: Preparation and Purification of Some Derivatives of Chlorophylls a and b [Internet]. Helsinki (Fi): ACTA Chemica Scandinavica; [cited 2013 Mar 9] Available from: actachemscand.org/pdf/acta_vol_27_p1771-1780.pdf Von Elbe as cited in Fennema OR. 1996. Food Chemistry. 3rded; New York, Marcel Dekker Inc. p. 653-673